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JP-7856598-B2 - Abrasive particle dispersion for polishing, method for manufacturing the same, and method for polishing semiconductors.

JP7856598B2JP 7856598 B2JP7856598 B2JP 7856598B2JP-7856598-B2

Inventors

  • 中山 和洋
  • 碓田 真也

Assignees

  • 日揮触媒化成株式会社

Dates

Publication Date
20260511
Application Date
20230314

Claims (8)

  1. Abrasive dispersion liquid for polishing, comprising silica fine particles that satisfy all of the following requirements [1] to [5] dispersed in a dispersion medium. [1] The average particle diameter measured by dynamic light scattering is between 5 nm and 500 nm. [2] The minor axis/major axis ratio measured by image analysis is 0.1 or greater and less than 0.8. [3] The carbon content is less than 150 ppm based on the silica content. [4] Solid 29. In the Si-NMR spectrum, when the peak area originating from Si(OSi) 4 is defined as Q4 and the peak area originating from HO-Si(OSi) 3 is defined as Q3 , the peak area ratio of Q4 / Q3 is between 1 and 30. (However, the chemical shift is based on tetramethylsilane as the reference substance, with Q4 being a peak in the range of -110 ppm to -120 ppm and Q3 being a peak in the range of -100 ppm to -110 ppm.) [5] When the peak near 3740 cm⁻¹ in the FT-IR measurement at 300°C using the vacuum heating transmission method is defined as P1 300 and the peak near 3660 cm⁻¹ as P2 300 , and when the peak near 3740 cm⁻¹ in the FT-IR measurement at 110°C is defined as P1 110 and the peak near 3660 cm⁻¹ as P2 110 , the value obtained by subtracting the peak ratio of P1 110 / P2 110 from the peak ratio of P1 300 / P2 300 [(P1 300 / P2 300 ) - (P1 110 / P2 110 )] is 0.20 or more and 1 or less.
  2. The abrasive dispersion liquid for polishing according to claim 1, wherein, in the particle size distribution obtained by image analysis, the particle size at a cumulative frequency of 10% is defined as D10, the particle size at a cumulative frequency of 50% is defined as D50, and the particle size at a cumulative frequency of 90% is defined as D90, the condition expressed by the following formula (F1) is satisfied. 1.0≦[(D10+D90)/2]/D50≦1.4...(F1)
  3. The abrasive dispersion according to claim 1 or 2, wherein the Al concentration in the silica solid content of the abrasive dispersion is 20 ppm or less, the Ca, Ni, and Na concentrations are each 10 ppm or less, and the Mg, Ti, Cr, Fe, Cu, Zn, Ag, and Pb concentrations are each 5 ppm or less.
  4. A polishing abrasive dispersion according to claim 3, for use in polishing semiconductors.
  5. A method for polishing a semiconductor, comprising the step of polishing the semiconductor using the abrasive dispersion described in claim 4.
  6. A method for producing an abrasive dispersion according to claim 1, comprising the following steps [1] to [5]. Step [1] A step of preparing a compound solution by adding a suspension of silicon fine particles to an aqueous alkali hydroxide solution at an addition rate of 0.05 g/min·L or more and 5 g/min·L or less. Step [2] As soon as the temperature of the preparation liquid obtained in Step [1] reaches 60°C due to the dissolution reaction of silicon nanoparticles, a further silicon nanoparticle suspension is added to the preparation liquid at an addition rate of 0.05 g/min·L to 5 g/min·L, and then the liquid is held at a temperature of 60°C to 90°C for a period of 4 hours to 24 hours to obtain an alkali silicate solution. Step [3] A step to obtain a purified acidic silica solution by dealkalizing and demetallic ionizing the alkali silica solution obtained in step [2]. Step [4] A portion of the purified acidic silicic acid solution obtained in step [3] is added to an aqueous alkali hydroxide solution, heated at a temperature of 75°C to 98°C, maintained at a temperature of 75°C to 98°C for 30 minutes or more, and then a portion of the purified acidic silicic acid solution obtained in step [3] is added at an addition rate of 1 g/min·g to 200 g/min·g, and the temperature of 75°C to 98°C is maintained for 30 minutes to 9 hours, after which it is cooled to room temperature to obtain a silica nanoparticle precursor dispersion. Step [5]: The silica nanoparticle precursor dispersion obtained in Step [4] is heated to a temperature of 75°C to 98°C, maintained at a temperature of 75°C to 98°C for 30 minutes or more, and then a portion of the purified acidic silicic acid solution obtained in Step [3] is added at an addition rate of 1 g/min·g to 300 g/min·g, and the temperature of 75°C to 98°C is maintained at a temperature of 30 minutes to 9 hours, after which it is cooled to room temperature.
  7. The method for producing an abrasive dispersion according to claim 6, wherein the dealkalization and demetallic ion treatment in step [3] includes at least two cation exchanges, and the difference in pH value before and after the first cation exchange is 7 or more.
  8. The method for producing an abrasive dispersion for polishing according to claim 6, wherein the Al concentration relative to the silica solid content of the purified acidic silicic acid solution obtained in step [3] is 20 ppm or less, the Ca, Ni, and Na concentrations are each 10 ppm or less, and the Mg, Ti, Cr, Fe, Cu, Zn, Ag, and Pb concentrations are each 5 ppm or less.

Description

This invention relates to abrasive particle dispersions suitable as polishing agents used in the manufacture of various semiconductor devices. In particular, it relates to abrasive particle dispersions suitable for planarizing insulating films formed on semiconductor substrates by chemical-mechanical polishing, a method for producing the same, and a method for polishing semiconductors. Semiconductor devices such as semiconductor substrates and wiring boards achieve high performance through increased density and miniaturization to meet the demands for miniaturization, increased speed, and higher functionality of the electronic devices on which they are mounted. Because the surface condition of such semiconductor devices affects their semiconductor properties, chemical-mechanical polishing (CMP) is applied in the semiconductor manufacturing process. For example, it is used to remove excess oxide in shallow trench isolation (STI), and to planarize the interlayer insulating film when forming a wiring layer on top of an interlayer insulating film covering a wiring layer. Furthermore, it is an essential technique for removing tungsten films in contact plug polishing. It is also an essential technique for removing excess Cu films in the formation process of Cu damascene wiring. Generally, CMP abrasives consist of abrasive grains and chemical components. The chemical components promote polishing by oxidizing or corroding the target coating. The abrasive grains, on the other hand, perform polishing through mechanical action; colloidal silica, fumed silica, or ceria particles are commonly used as abrasives. In the shallow trench element separation process, not only the silicon oxide film but also the silicon nitride film is polished. To facilitate element separation, a high polishing rate for the silicon oxide film and a low polishing rate for the silicon nitride film are desirable; therefore, the polishing rate ratio (selectivity ratio) is also important. Conventionally, a method of polishing such components has been employed in which a relatively rough primary polishing process is followed by a precise secondary polishing process to obtain a smooth surface or an extremely high-precision surface with few scratches or other imperfections. Regarding abrasives used for secondary polishing as a finishing polish, the following methods have been conventionally proposed. Patent Document 1 discloses a silica sol in which silica fine particles are dispersed in water, wherein the average secondary particle diameter of the silica fine particles is 20 to 1000 nm, the average particle diameter of the secondary particles is 1.5 to 3.0 times the average particle diameter of the primary particles, the metal impurity content is 1 ppm or less, and the silica concentration is 10 to 50% by weight. When this silica sol is applied to semiconductor polishing applications, while it meets the requirements for metal impurities, it may contain unreacted substances such as silicon alkoxide oligomers that do not grow into silica particles, and may contaminate the substrate being polished. Furthermore, because the reaction of silicon alkoxide oligomers and other substances is insufficient, the inside of the particles is sparse, resulting in insufficient particle hardness, and consequently, an insufficient polishing speed for polishing applications. On the other hand, the two main methods for producing colloidal silica to date are the water glass method and the alkoxide method. The water glass method involves ion-exchange of sodium silicate to prepare activated silicic acid, which is then added to an aqueous solution containing seed particles whose pH has been adjusted with NaOH under heating to allow particle growth (see Patent Document 2). This method makes it possible to obtain particles with a relatively dense structure. The alkoxide method is a so-called Stober method, which produces silica particles by hydrolyzing alkyl silicate (tetraalkoxysilane) in the presence of a basic catalyst while simultaneously carrying out condensation and particle growth. This method makes it possible to prepare colloidal particles ranging from nanoscale to micronscale. For example, a method for producing cocoon-shaped colloidal silica has been proposed, characterized by adding methyl silicate (tetramethoxysilane) or a mixture of methyl silicate and methanol dropwise over 10 to 40 minutes under stirring in a mixed solvent consisting of water, methanol, and ammonia or ammonia and an ammonium salt, and reacting the methyl silicate with water to produce colloidal silica having a short diameter of 10 to 200 nm and a long diameter/short diameter ratio of 1.4 to 2.2 (see Patent Document 3). In addition, a method for producing cocoon-shaped colloidal silica is known, characterized by hydrolyzing a tetramethoxysilane tetramer dropwise in a mixture of methanol, water, and ammonia (see Patent Document 4). Furthermore, a method for producing silica sol in which elongated a